The present invention relates to an apparatus for processing materials, and in particular to an apparatus for processing particles with nanoscale cross-section such as carbon nanotubes in order to form circuits or devices.
Carbon exists as a number of different allotropes, for example diamond and graphite. Despite both of these materials being formed from carbon atoms they have very different physical and electrical properties. Carbon can also form allotropes having a spherical shape, known as fullerenes, or a sheet formed from a single layer of graphite molecules, called graphene. Carbon can also be processed such that it has a cylindrical nanostructure and this allotrope is called a carbon nanotube (CNT). The size of a CNT and the geometry of the carbon atoms in the CNT will determine the properties of a CNT. It has been demonstrated that carbon nanotubes can be fabricated in large quantities and with specific diameters and chirality that means that they have the properties of metallic conductors. It is thought that significant advantages in electrical and physical characteristics can be realised for wires manufactured from such CNTs. For example, it is theoretically predicted that such CNT wires will have lower resistivity than copper or silver conductors and that they will not be subject to the skin effect that is present in copper conductors, which leads to a decreased performance as the frequency of an AC current passed through them increases. In addition it has been demonstrated that CNTs can be used for data transmission. Physically, CNT wires have been demonstrated to be highly flexible and extremely strong and therefore suited to fabrication into very fine but robust structures.
Furthermore, it is believed that it may be possible to manipulate CNTs in order to fabricate simple structures, such as nanowires having very precise dimensions (for example, for use in high-frequency circuits), or more complex structures such as devices for use in electronic or photonic circuits.
There is a trend towards miniaturization of electronic circuit components which ideally requires individual macromolecules and nanoscale particles. The technical challenge lies in assembling individual nanotubes into a precise controlled configuration onto a substrate. Carbon Nanotubes are one example of a modern nanoscale material which is suitable for this application; both as interconnects and transistors. However this invention is applicable to other forms of nanotube, nanowire and nanoscale particle.
According to a first aspect of the present invention, there is provided an apparatus comprising: a chamber; an inlet for admitting particles dispersed within a fluid into the chamber; a template, configured such that, in use, particles passing through the template are selectively deposited on a substrate received adjacent to the template; a charging element, the charging element extending across the chamber and being located between the inlet and the template such that, in use, the charging element can impose an electrical charge on the particles admitted into the chamber; and a filter element, the filter element extending across the chamber and being located between the charging element and the template such that, in use, a first electrical signal is applied to the filter element such that the particles are attracted to the filter element.
The template may comprise a single or a plurality of template regions each of which is a nanopore membrane configured with a distinct pattern of pores/holes, which may be received within a frame formed from an insulating material. Furthermore, an electrical potential may be selectively applied to one or more of the plurality of template regions.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: